The present invention relates to a method for controlling a synchronous machine and to a control apparatus for a synchronous machine. The present invention further relates to an electric drive system.
Document WO 2010 043 454 Al discloses a method and an apparatus for the field-oriented control of a synchronous machine. For this purpose, a transverse current setpoint value, a longitudinal current setpoint value, a transverse current actual value and a longitudinal current actual value are identified. In this case, the transverse current serves to form the torque of the machine, while the longitudinal current serves to form the field or to weaken the field. Said values are fed to a controller, which identifies a longitudinal voltage component and a transverse voltage component. These are converted to voltages of a polyphase three-phase voltage system and then passed on to a pulse-controlled inverter. Furthermore, the stator currents of the machine are detected and, with knowledge of the rotor position angle, converted to the longitudinal and the transverse current actual value. The synchronous machine is controlled by the output signals of the pulse-controlled inverter.
Converter-fed synchronous machines are generally operated by way of sinusoidal currents independently of the form of their voltage induced by the excitation field. Initial voltage control for introducing said sinusoidal currents also takes place here in a sinusoidal manner. Deviations from the sinusoidal shape in the voltage induced by the excitation field can lead to disturbances in the current profile. These can be balanced, for example, by way of a disturbance variable observer. In this way, a virtually sinusoidal current profile is impressed into the synchronous machine in any case.